﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace StingBuilderExtTest
{
    static class StringBuilderExtensions
    {
        public static StringBuilder Substring(this StringBuilder sb, int index, int length)
        {
            StringBuilder result = new StringBuilder();
            for (int i = 0; i < length; i++)
            {
                result.Append(sb[index + i]);
            }
            return result;
        }
    }
}
